AS 3959-2009 is now superseded by AS 3959-2018, but the focus is still on preventing fire from entering the building envelope, rather than on preventing its spread internally. So there are no restrictions on internal wall construction, nor on the internal face of an external wall. Regarding FRL's associated with external walls, in BAL-FZ one of the options for a timber-framed external wall is to utilise a system with an FRL of -/30/30 when tested from the outside. Such a system would also satisfy external wall requirements in a lower BAL (clause 3.4).

Our Technical Design Guide no. 21 titled Domestic Timber Deck Design will be a useful reference,  available for download free of charge via this link https://www.woodsolutions.com.au/publications. The three timber species you mention are all 'durable' in both senses of the term - ie. wear resistance and rot resistance. All three fall into Durability Class 1 in terms of AS 5604, Timber - Natural durability ratings when placed in above-ground situations.

Oriented Strand Lumber (OSL), more commonly termed Oriented Strand Board (OSB), is not marketed as a structural product and hence doesn't have a stress grade according to the Australian system. Strength properties are contained in a US document available via this link https://www.pfsteco.com/techtips/pdf/tt_osbdesigncapacities.

AS 1530.3 is titled Simultaneous determination of ignitability, flame propagation, heat release and smoke release. These values are collectively known as the ‘Early Fire Hazard’ properties. For blackbutt the numbers are: Ignitability 13; Flame Propagation 6; Heat Release 5; and Smoke Release 3.

The National Construction Code (NCC) aims to 'compartmentalise' fire, ie. contain it within a dwelling occupancy or 'fire compartment'. A fire compartment is defined as any part of a building separated from the remainder by barriers to fire such as walls and/or floors having an appropriate resistance to the spread of fire with any openings adequately protected (NCC 2019 p. 649). It follows that internal non-loadbearing walls are not caught up by the regulations, and timber is permitted without the need for fire resistant linings.